Waterproofing of leathers



Dec. 13, 1960 R. J. HOL'ZINGER ET AL 2,964,425 WATERPROOFING OF LEATHERSFiled April 29, 1958 54 R00 SINE DE RI VED COMPOUND INVEN TORS RUDOL PHJ HOZZI/VGER L I A r TOR/VEY GEORGE M. WHEL/J/V JAM 1 A 0 N 6% M W m E 0A N E l 9 w w m m G ART 7, SMW 0 L M L/ United States PatentWATERPROOFING OF LEATHERS Rudolph J. HolzingerfNorth Merrick, and GeorgeM. Whelan, New York, N.Y., assignors to Socony Mobil Oil Company, Inc.,a corporation of New York Filed Apr. 29, 1958, Ser. No. 731,642

12 Claims. (Cl. 117-142) This invention relates to the treatment ofleathers, particularly such leathers as upper leathers, to decreasetheir permeability to water without detrimental effect upon otherdesirable properties.

It is desirable, in the preparation of leathers designed for use in theuppers of shoes, particularly for armed services and heavy duty uses inworking and field conditions, to have a high degree of waterproofness.At the same time, it is almost imperative to retainthe porosity andflexibility of the leather. Porosity not only permits breathing withconsequent avoidance of the sweating and resultant foot troubles arisingfrom con-' tinuous wearing of moisture vapor impermeable'footgear, butporosity contributes to some extent to'the'insulating capability of theleather. The problem is complicated by the fact that water may pass notonly through such natural porosity as may exist, but also, due to thehydrophilic nature, of leather fibers, each fiber may become a duct forthe passage of water.

The usual approach to this problem has been by stuffing theleather withoils, greases or waxy materials during preparation of the leather, byimpregnating the leather during manufacture with plastic or rubber-likematerials, or by applying a dubbing or other waterproofing material tothe finished leather article. Not only do these treatments, if heavyenough to fill the pores, reduce the breathing capability of theleather, but in most cases they achieve no correction of the hydrophilicnature of the leather fibers themselves. Treatments applied to thefinished articles are seldom thorough enough to stop even mechanicalleakage. All fail to a great degree when the leather is subjected to thecontinuous flexure which occurs when the shoes are worn.

Anobject of the present invention is to provide a leather substantiallywaterproof under continuous flexure which still has a porositysuflicient to permit breathing.

Another object of this invention is to provide a leather in which thehydrophilic nature of the leather fibers is sufficiently suppressed toprovide waterproofness without the sacrifice of porosity, whichcondition will permit breathing under use conditions in a leather thatremains soft and flexible.

An important obiect is the provision of a waterproofing'treatment thatmay be applied without stuffing or, alternatively, may be applied aspart of a stufling op? eration so conducted as to confer waterproofness,to give to the leather such desirable properties as may arise from thejudicious controlled use of stufling compounds, and at the same timepreserve the porosity, softness and flexibility of the leather underconditions of use.

-' All of these objects may be achieved by the use of certain sarcosinecompounds which are more specifically described hereinafter, thecompounds being generally aliphatic amino carboxylic acids having highersaturated or unsaturated aliphatic acid radicals directly attached tothe nitrogen atom. The invention applies generally to chrome tanned andvegetable tanned leather but is found to be especially useful in thetreatment of chrome retanned 2,964,425 Patented Dec. 13, 1960 iceleather. While the compounds of this invention can be used alone, theyare generally mixed to some extent with a stufling grease and applied tothe leather as a mixture by the standard stufling procedure well knownto workers in this field. The quantity of the material to be used isusually calculated as a fixed percentage by weight of the leather to betreated. A leather stuffed with a mixture of 50 percent of the materialof this invention and 50 percent stuffing grease would mean, therefore,that if the leather were, for example, 30 percent stuffed with themixture, it would contain about 15 percent active Waterproofing agent.The optimum amount of the mixture used depends upon a balance of cost,waterproofing required and appearance of the finished leather desired.

The invention will be disclosed more fully in following detaildescription and in the attached figures.

Figure 1 shows a conventional stuffing drum in crosssection with asample of leather being treated with the compound of this invention.

Figure 2 shows a portion of a treated leather strip in cross-section.

Referring to Figure l, the conventional stuffing drum is depicted. Thecylindrical drum is mounted on its axis in a horizontal position and'thedrum is rotated by suitable driving means such as an electrical motorthrough a conventional gear train. The leather and treating compound areintroduced into the drum through the lid. The rotation of the drumcauses the treating compound to be worked into the leather by carryingthe hide up near the top, permitting it to fall back into'the pool oftreating compound. After a suitable period of treatment, the

' treated leather is removed.

Referring to Figure 2, it is seen that the collagen fibre bundles areseparated from each other allowing the leather to breathe. 1 Inuntreated leather the porous collagen fibre bundles act as Wicks andcause water to penetrate into and through the leather by capillaryaction. The'waterproofing compound of this invention is shown on Figure2 asa coating layer surrounding each collagen fibre bundle. It is seenthat the coating material prevents the transfer of liquid water andblocks the Wick ing action. However, the pores of'the leather remainopen, allowing the transfer of air and water vapor and hence normalbreathing techniques.

An accepted method of test for the efliciency of waterproofing treatmentof upper leathers and the like is the so-called Maeser Test, developedin the leather labora-. tory of the National Bureau of Standards tosimulate conditions of natural use, and reported by Meith Maeser in theJournal of the American Leather Chemists Association, vol. XLII, page401 et seq., August 1947. In short, it consists of mechanically flexinga sample ofleather, cons rained in the form of a trough, in contact uponone side with water, either for a preset number of flexes; and measuringthe water that has penetrated through the leather, or more usually,noting the number of flexes required before water appears upon the dryside. An-

other test method, commonly referred to as the Dow Corna necessity ofconstant operator attention when testing high- 1y resistant leatherswith the Maeser water pentration' machine, this method for automatic endpoint determination was developed. This method is similar to the DowCorning Test in that it is based on the sudden change.

in the electrical resistance between the inside and the.

outside of the leather at the instant that some point is completely wetthrough. The method used is reported by Meith Maeser and Robert M.Lollar in the Journal of the American Leather Chemists Association, vol.LI, page 377 et seq., July 1956. This test was selected and the resultsreported hereinafter are test results obtained in accordance with thismost recent test procedure. The test reports the percentage of waterpicked up after a fixed number of flexes as indicating waterproofingability even though penetration has occurred.

The waterproofing compounds with which this invention is concerned arethe free aliphatic acids of the folterial Sarkosyl-O, oleyl sarcosine;

wherein R is a radical of a higher aliphatic acid of from 12 carbonatoms to 22 carbon atoms, saturated or unsaturated. Of these materials,the unsaturated aliphatic acids of from 16 to 18 carbon atoms arepreferred. A particularly preferred compound is the commercial materialSarkosyl-O, oleyl carcosine;

and the corresponding stearoyl sarcosine sold under the trade nameSarkosyl-S.

CnHas--N-CHz-C O OH (3H5 Examples illustrating the invention are asfollows:

Example I A sample of retanned leather was treated with oleyl sarcosinein accordance with well known stulfing procedures, being stuffed toabout 30 percent of the weight of the test leather specimen. Oleylsarcosine is primarily an oleic sarcosine compound with a minor amountof closely related sarcosine compounds and other unsaturates. Themolecular weight of oleyl sarcosine is 340-350, color (FAC) 10, settingpoint 0 C., specific gravity 0.948 and solubility is miscible withstoddard solvent at 25 C. The sample was then tested in accordance withthe E-Z modified Maeser test procedure (Journal of the American LeatherChemists Association, July 1956) for 10,000 cycles without showing anysign of water emergence through the leather. The total water picked upby the test specimen was 3.1' percent of the weight of the leatherspecimen. When using this E-2 end point test procedure with cleanleather not treated with the waterproofing material of this invention,water shows through the leather in about -20 flexes and at least by 100flexes, the leather is completely saturated. It is clear, therefore,from these results, that oleyl sarcosine is an outstanding-compound foruse in rendering leather waterproof.

Example II A sample of retanned leather was treated with cocoylsarcosine (available under the trade name Sarkosyl LC). This material isapproximately 2 percent capric, 55 percent lauric, 22 percent myristicand 21 percent stearic compounds, in other words, carbon chains of aboutC C The leather sample was stuffed to about 30 percent by weight andtested in accordance with the E-2 procedure. The sample showed waterpenetration at 495 flexes, 6.34 grams of water being absorbed by thetest' sample at that point. The test was continued to 5,000 cycles andshowed a water pick-up of about 23 percent of the weight of the leathersample.

Example III A sarcosine largely saturated C and C in approximately equalproportions was tested, using the same test procedure as used inExamples I and II. This test-sample showed water penetration at 101flexes with a water absorption of 8.77 grams of water. The test wascontinued for 5,000 cycles and was then found to have picked up onlyabout 33 percent water by weight of the leather sample. It is seen thatthe compounds of Examples II and III, while passing water to some extentat a rather low number of cycles, do have the capacity for substantiallylimiting the amount of water that is picked up by the leather.

Example IV A twelve carbon sarcosine, lauroyl sarcosine, being aboutpercent lauric and the remainder myristic, palmitic and oleic sarcosinecompounds, was tested according to the test procedure used for ExamplesI-III. This material is available under the trade name Sarkosyl L. Thistest sample showed water penetration after 175 flexes and absorbed 7.85grams. At the end of 5,000 flexes the sample had picked up 30 percentwater by weight of leather test sample.

The examples given hereinabove demonstrate the efficacy of the indicatedcompounds when applied alone as a waterproofing agent.

It is also to be noted that these compounds are competent waterproofingagents when applied with, or as part of, more conventional treatments,such as in stufling or fat liquoring.

For example, a quite conventional stuffing grease may be made up ofequal parts of beef tallow and a paraffin wax of -127 F. melting point,as is well known in the art. The waterproofing agents herein disclosedmay be admixed with this stuffing grease, to the extent of from about 10percent to about 75 percent of the mixture, usually preference being hadfor waterproofing agent concentrations ranging from about 25 percent toabout 50 percent by weight of the stuffing mixture. Application of suchstufling mixtures not only achieves a satisfactory degree ofwaterproofing, but also gives those desirable features arising from theuse of the conventional agents, both in the process and in the finishedleather.

Example V The oleyl sarcosine, previously described with respect toExample I, was mixed in equal parts with a stufiing grease and theleather sample was stuffed to about 30 percent of the weight of theleather. The sample was then tested in accordance with the E-2 testprocedure. The sample showed water penetration at 108,840 flexes, 4.71grams of water being absorbed by the sample at that time. At 110,000flexes the leather had picked up only 13 percent water by weight of theleather, demonstrating the outstanding waterproofing ability of thiscompound.

Example VI The oleyl sarcosine was mixed with stufling grease in theproportion of 25 percent sarcosine compound to 75 percent stuffinggrease. The leather sample was stuffed to about 30 percent of the weightof the leather and tested in accordance with the 13-2 test proceduredescribed hereinabove. The. sample showed water penetration after 51,360flexes, 7.49 grams of water being absorbed. At 100,000 flexes theleather sample had picked up only 25 percent water by weight of theleather.

The examples given hereinabove are not to be considered limiting, butare supplied merely to illustrate the invention. The invention is to beconstrued broadly, the limitations intended being those of theattachedclaims.

We claim:

1. The method of making leather resistant to water penetration whichcomprises introducing into the leather a compound ofthe formula whereinR is an aliphatic acyl radical of 16 to 22 carbon atoms, 1

2. The method of making leather resistant to water penetration whichcomprises introducing into the leather a compound of the formulaR-rf-om-o 0 on wherein R is an aliphatic acyl radical of 16 to 18 carbonatoms.

3. The method of making leather resistant to water penetration whichcomprises introducing into the leather a compound of the formulaR-N-CHr-COOH wherein R is an unsaturated aliphatic acyl radical of 16 to22 carbon atoms.

4. The method of making leather resistant to water penetration whichcomprises introducing into the leather a compound of the formula whereinR is a saturated aliphatic acyl radical of 16 to 18 carbon atoms.

5. The method of making leather resistant to water penetration whichcomprises introducing into the leather a compound of the formulaGnHu-f'l-N-CH,-CO0H 6. The method of making leather resistant to waterpenetration which comprises introducing into the leather a compound ofthe formula 7. As an article of manufacture a leather impregnated with arelatively small amount, sufiicient to impart water resistance to theleather, of a compound of the formula R-N-CHa-COOH wherein R is analiphatic acyl radical of 16 to 22 carbon atoms.

9. The claim 7 further characterized in that the radical R is ll(Jr-(Harc- 10. The claim 8 further characterized in that the radical Ris 11. The claim 7 further characterized in that the radical R is 12.The claim 8 further characterized in that the radical R is ll CnHu-CReferences Cited in the file of this patent UNITED STATES PATENTS2,047,066 Gleitenberg July 7, 1936 2,047,069 Hentn'ch et a1 July 7, 19362,293,844 Maxwell Aug. 25, 1942 2,689,170 King Sept. 14, 1954 2,700,625Morris et al. Jan. 25, 1955 2,825,660 Roux Mar. 4, 1958 2,830,064 MonickApr. 8, 1958 2,841,573 Ahlbrecht et a1. July 1, 1958 UNITED STATESPATENT OFFICE CERTIFICATION OF CORRECTION Patent No., 2,964,425 December13, 1960 Rudolph J. Holzinger et alo It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below Column 3, line 13 forvterial Sarkosyl-O, oleyl sarcosiner" read lowing generalconfiguratlonr, llne 22, for "carcosine" read sarcosine Signed andsealed this 13th day of June 19610 (SEA L) Attest: ERNEST W. SWIDERDAVID L. LADD Attesting Officer Commissioner of Patents

1. THE METHOD OF MAKING LEATHER RESISTANT TO WATER PENETRATION WHICHCOMPRISES INTRODUCING INTO THE LEATHER A COMPOUND OF THE FORMULA